A serial port is an interface that can be used for serial communication. Serial communication involves the transfer of information one bit at a time. Serial ports are general-purpose interfaces that can facilitate information exchange with a wide variety of devices including modems, computing devices, and pointing devices.
Computing devices use serial controllers to control the flow of information through a serial port. Most serial port controllers use a universal asynchronous receiver-transmitter (UART) to transmit and receive information through a serial port. A computing device can be a mainframe computer, desktop computer, laptop computer, personal digital assistant, server, blade server, client, router, switch, or similar device. The term “system” is used as a shorthand for a computing device or part of a computing device. A blade server is a computing device form factor wherein a single module contains components such as processors, memory devices, and network connections that are found on multiple boards in conventional servers. A blade chassis supports multiple blade modules and provides a backplane through which the blade modules get connections to input/output interfaces and power.
A management controller controls and monitors the management features of a computing device. For example, the management controller may use one or more sensors to monitor temperature, voltage, fan, and chassis intrusion within a computing device. The management controller autonomously monitors system management events (e.g., over-voltage or over-temperature) and typically logs the occurrence of the events into non-volatile memory in a predefined format (e.g., a sensor error log). Management controllers can also be polled to determine the current monitored status of a computing device. Alternatively, management controllers can be configured to automatically send an alert message when an error condition is detected either manually or by software running within the management controller.
FIG. 1 is a block diagram of selected components of conventional computing device 100. Conventional computing device 100 includes serial port 110, network interface 115, management controller 120, and serial controller 130. Serial controller 130 exchanges serial information with the serial port through receive information line 150 and transmit information line 155. Handshake signals 156 control the flow of transmit and receive information. Management controller 120 and serial controller 130 connect to other elements of conventional computing device (not shown) through communication channels 175 and 180 respectively.
Serial port 110 uses communication channel 160 to exchange information with one or more remote devices. Typically, serial port 110 complies with the Electronic Industries Association Recommended Standard-232 entitled, “Interface Between Data Terminal Equipment and Data Communications Equipment Employing Serial Binary Data Interchange” (RS-232 standard) or a similar standard governing serial communications between computing devices. Communication channel 160 may connect with a remote computing device to facilitate the exchange of management information between the remote computing device and computing device 100.
Management controller 120 connects with network interface 115 through communication channel 185. Network interface 115 may be an Ethernet interface, Token Ring interface, Fiber Channel High Speed interface, Fiber Distributed Data Interface or the like. Network interfaces are well known to one of ordinary skill in the art and will therefore not be further described except as they relate to embodiments of the invention. Computing device 100 may use communication channel 170 to exchange management information with one or more remote computing devices.
FIG. 1 illustrates that conventional computing systems typically employ more than one communication channel (e.g., channels 160 and 170) to exchange information with remote computing devices. Using multiple communication channels increases the number of physical cables that attach to computing device 100. Computing device 100 may be, for example, in a rack containing dozens of servers, or may be used as a blade server in a rack containing dozens (or hundreds) of other blade servers. Clearly, any increase in the number of physical cables connecting to each computing device increases the cost and complexity of the overall system.